Body Fat Estimate Calculator — US Navy Method (UK)
Instantly estimate your body fat percentage, lean mass, and fat mass using the globally recognised US Navy Method. Accurate, simple, and optimised for UK metric measurements.
Men’s or Women’s Calculation?
The US Navy Method uses slightly different anatomical measurements for men and women to ensure maximum accuracy. Select your profile below.
Men’s Body Fat Calculator
Enter your measurements in centimetres (cm) and weight in kilograms (kg)
Measure just below the larynx (Adam’s apple).
Measure at the navel (belly button) level.
Body Composition Result
Estimated body fat percentage and mass breakdown
Enter your measurements, then click Estimate Body Fat.
Women’s Body Fat Calculator
Enter your measurements in centimetres (cm) and weight in kilograms (kg)
Measure just below the larynx, tape sloping slightly downward.
Measure at the narrowest point of the waist.
Measure at the widest point of the hips/buttocks.
Body Composition Result
Estimated body fat percentage and mass breakdown
Enter your measurements, then click Estimate Body Fat.
Body Fat Percentage Categories
General guidelines for body fat percentage categories for adults. Note that “essential fat” is the minimum amount required for basic physiological function.
| Category | Women (%) | Men (%) |
|---|---|---|
| Essential Fat | 10 – 13% | 2 – 5% |
| Athletes | 14 – 20% | 6 – 13% |
| Fitness | 21 – 24% | 14 – 17% |
| Average / Acceptable | 25 – 31% | 18 – 24% |
| Obese | 32%+ | 25%+ |
Body Fat Calculator FAQ
Everything you need to know about using the Navy Method to estimate your body composition accurately.
The US Navy Method uses simple tape measurements (height, neck, waist, and hips for women) in a mathematical formula to estimate body density, which is then converted to a body fat percentage. It is widely used by militaries and fitness professionals globally, including in the UK, due to its high correlation with DEXA scans.
For men, you need your height, neck circumference, waist circumference (at the navel), and weight. For women, you need height, neck circumference, waist circumference (at the narrowest point), hip circumference (at the widest point), and weight. All measurements should be in centimetres (cm) and kilograms (kg).
The Navy Method is generally accurate within 3-4% of a DEXA scan (the gold standard) when measurements are taken correctly. Accuracy depends heavily on using a flexible, non-stretch tape measure and keeping the tape parallel to the floor without pulling it too tight.
For adult men, a healthy ‘fitness’ range is typically 14-17%, while ‘average’ is 18-24%. For adult women, ‘fitness’ is typically 21-24%, and ‘average’ is 25-31%. Essential fat (the minimum required for basic physiological function) is 2-5% for men and 10-13% for women.
This calculator is optimised for the UK metric standard (centimetres and kilograms). If you have imperial measurements, we recommend converting them first (1 inch = 2.54 cm, 1 lb = 0.453 kg) for the most accurate results, as the underlying formula is calibrated for metric inputs.
If your waist measurement is smaller than or equal to your neck measurement, the Navy formula cannot calculate a valid result (it requires waist > neck for men, and waist + hip > neck for women). This typically indicates a measurement error. Please remeasure, ensuring the tape is snug but not compressing the skin.